Ideally, you should have a smoke detector on every level of the house, including the basement. It is recommended to place your detectors at the top of each stairway, outside, and inside the bedrooms. Now, whether your hang them on the wall or on the ceiling, that depends on which type you buy. Be sure to read the manufacturer's recommendations on where to place.
Be sure not to place them near anything that will interfere with their sensing. Do not place near a furnace, heating appliance, anything that exudes humidity or excess moister, or near windows and vents.
How To Install
Installing an alarm is easy. Most alarms already come with a mounting rack. Screw in your mounting rack, insert battery, and screw on to the mount. It is that easy.
Test Monthly - Each detector has a test button right on top.